What is a Calibration Weight Class?
Each class of weights represents a specific level of accuracy, with higher classes indicating greater precision. In metrology, the scientific study of measurement, weight class plays a vital role.
Choosing the Right Calibration Weight Class
Choosing the right weight class is like selecting the right clothing size. Just as a snug fit (Class 0) is necessary for formal occasions where precision matters, a looser fit (Class 6) might be acceptable for casual wear where some flexibility is allowed.
What is a Tolerance and how is it determined?
Weight tolerance is the difference between the maximum and minimum values of a given nominal value. Weight tolerance tells you how much deviation is allowed in the mass of the weight, adhering to the standard weight classification set by governing bodies. The weight tolerances for each class are determined by the governing bodies that oversee national and international weighing standards. The primary organizations are ANSI/ASTM and OIML (International Organization of Legal Metrology).
A higher precision weight class such as ANSI/ASTM Class 1 will have a low tolerance, meaning the weight closely matches its specified value. A lower precision class such as ANSI/ASTM Class 6 will have a larger tolerance, meaning the weight is close to its nominal value but may deviate more than a high precision class.
For example, here are the “In-Tolerance” ranges for a 100 gram weight:
|
Class |
Nominal Value |
Weight Tolerance |
“In-Tolerance” Range |
|---|---|---|---|
|
ANSI/ASTM Class 1 |
100 g |
0.025 mg |
99.999975 g – 100.000025 g |
|
ANSI/ASTM Class 6 |
100 g |
10.0 mg |
99.990 g – 100.010 g |
And here are all the Tolerance values for a 100 gram weight:
|
ANSI/ASTM Class |
000 |
00 |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
|---|---|---|---|---|---|---|---|---|---|---|---|
|
0.025 mg |
0.05 mg |
0.13 mg |
0.25 mg |
0.50 mg |
1.0 mg |
2.0 mg |
9 mg |
10 mg |
100 mg |
||
|
Troemner |
UltraClass |
|
|---|---|---|
|
0.13 mg |
||
|
OIML Class |
E0 |
E1 |
E2 |
F1 |
F2 |
M1 |
M2 |
M3 |
|
|---|---|---|---|---|---|---|---|---|---|
|
0.025 mg |
0.05 mg |
0.16 mg |
0.5 mg |
1.6 mg |
5 mg |
16 mg |
50 mg |
||
Selecting a Weight Class
To select the appropriate calibration weight class, the user must first determine the exact intended use of the weight. Understanding how to determine what class of calibration weight is necessary for ensuring accurate measurements. The application and weighing devices/balances in the laboratory need to be reviewed.
Remember, choosing the right weight class is like selecting the right clothing size. For example, in high-stakes environments such as pharmaceuticals or laboratories, using a Class 0 weight is essential. This is akin to wearing a tailored suit for a formal event—every detail must be perfect to ensure everything functions smoothly. Conversely, in less critical scenarios, such as routine production processes, a Class 6 weight may suffice, like wearing comfortable jeans for a casual outing.
Below are guidelines for a variety of markets and industries where weighing is an important process that requires control. When in doubt, select a weight class with a tighter/more precise tolerance to ensure the process meets the measurement control requirements.
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Markets and Industries |
ANSI/ASTM E617 Recommended Classes |
OIML R111 Recommended Classes |
|---|---|---|
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* Troemner offers the exclusive UltraClass Series – two-piece construction weights which meet or exceed ANSI/ASTM Class 0 one-piece construction requirements including tolerance. The benefit of UltraClass two-piece weights is the ability to adjust into tolerance during re-calibration service.
Balances and Weight Classes
Like calibration weights, balances and scales are classified according to an accuracy class based on the readability (resolution) of the device. This highlights the importance of calibration weights classifications in achieving accurate measurements.
The most precise balances need to be verified with the most precise calibration weights. Selecting the correct weight class is dependent on the accuracy needed to satisfy specific process tolerances and limits. When in doubt, select a more precise weight class to minimize risk in the weighing process.
|
Type of Balance |
Readability of Balance (d) |
ANSI/ASTM E617 Recommended Classes |
OIML R111 Recommended Classes |
|---|---|---|---|
|
Ultra Micro Balance |
d = 0.0000001 g d = 0.0001 mg |
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Micro Balance |
d = 0.000001 g d = 0.001 mg |
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Semi-Micro Balance |
d = 0.00001 g d = 0.01 mg |
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Analytical Balance |
d = 0.0001 g d = 0.1 mg |
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Precision Balance |
d = 0.05 g to 0.001 g d = 0.1 mg |
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Medium Balance |
d = 1 g to 2 g |
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Ordinary Balance |
d > 5g |
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In conclusion, just as you wouldn’t wear an ill-fitting outfit for a job interview, using the wrong weight class can lead to inaccuracies in measurement. Calibration ensures that your measurements align with the required standards, maintaining the integrity of your data. By understanding the parallels between weight classes and clothing sizes, you can make informed choices that enhance the accuracy of your measurements, ensuring that you always have the right fit for the job at hand.
Related Topics
ASTM, OIML, NIST, and Troemner UltraClass Calibration Weight Classes Understanding Calibration Weight Tolerances Understanding Calibration Weight Uncertainties Key Differences in Mass vs. Weight for Accurate Lab MeasurementsFor personalized advice on selecting the right calibration weights for your application, call, click, or tap to contact our expert team today!